The present invention relates generally to printing presses and more particularly to plate cylinders for printing presses.
Japanese Patent Application No. 2000-954 A shows a printing plate cylinder with a cylinder body and a shell mounted to a reduced diameter portion of the cylinder body for independent movement of the shell in order to adjust the lateral and circumferential register of a printing plate mounted to the shell with respect to the printing plate mounted on the cylinder body on the other side of the printing plate cylinder. The shell has a uniform thickness.
Commonly-owned European Patent Application No. 1 913 059 discloses a plate cylinder in which shells are movable with respect to a cylinder body using axially-extending arms gripping the underside of the shells, and corresponds to U.S. patent application Ser. No. 09/675,494, which is hereby incorporated by reference herein.
Commonly-owned German Patent Application No. 101 35 506 discloses a plate cylinder in which a shell is axially movable but circumferentially fixed with respect to a cylinder body, and corresponds to U.S. patent application Ser. No. 09/627,639, which is hereby incorporated by reference herein.
An object of the present invention is to provide a shell with space for a plate clamping device while minimizing loss of stiffness of the cylinder body. Another alternate or additional object of the present invention is to provide a splined shell connection with a cylinder body in which circumferential register is permissible.
The present invention thus provides a plate cylinder comprising a cylinder body having a cylinder body outer surface for a first image to be printed and a first end, and a shell having an inner surface circumferentially disposed about the first end and having a gap for holding a printing plate, the shell being axially moveable with respect to the first end and having a shell outer surface for a second image to be printed, the inner surface having at least one projection directed inwardly, the gap extending into the projection.
Since gaps for holding printing plates often require a substantial lock-up mechanism, the present invention permits sufficient space for the gap in the projection, while advantageously still permitting a thin shell thickness in other locations.
Preferably, the shell is at least partially circumferentially movable with respect to the cylinder body.
The at least one projection may include a plurality of projections. If more than one printing plate is supported by the shell, a gap may be located in each projection. Preferably, the projections are spaced symmetrically in the circumferential direction.
The cylinder body preferably has at least one outwardly projecting protrusion, and most preferably more than one of such protrusions. Preferably, the projection of the shell fits between two protrusions of the cylinder body. The protrusions may define a space into which the projection fits, the space preferably being wider than the projection, so that the shell is circumferentially movable with respect to the cylinder body.
The cylinder body may have a second end, with a second shell supported on the second end in a similar manner to the first shell.
A lock-up device is preferably located in the gap.
The present invention also provides a plate cylinder comprising a cylinder body having cylinder body outer surface for a first image to be printed and a first end with at least one outwardly-projecting protrusion having a first side and second side defining a space therebetween, and a shell having an inner surface circumferentially disposed about the first end and having a gap for holding a printing plate, the shell being axially moveable with respect to the first end and having a shell outer surface for a second image to be printed, the inner surface having at least one projection directed inwardly to fit into the space, the space being wider than the projection so as to permit circumferential movement of the shell with respect to the first end.
Preferably, a first and a second protrusion are provided, with the first side on the first protrusion and the second side on the second.